Methods and systems of advanced yaw control of a wind turbine

ABSTRACT

Embodiments of the present disclosure include a retrofit auxiliary nacelle yaw position control system that enables advanced nacelle yaw position control of a wind turbine by comparing a desired nacelle yaw position signal with the actual nacelle yaw position and generating a virtual relative wind direction signal that is provided to the existing turbine control unit. This method and system enable implementation of wake steering, collective yaw optimization and dynamic yaw optimization of a collection of wind turbines referred to as a wind plant. Modification of the existing turbine control unit is not required, greatly simplifying the implementation process of advanced yaw control strategies on existing wind plants.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 17/361,365, filed Jun. 29, 2021, which is anon-provisional of and claims priority to U.S. Patent Application No.63/108,532, filed Nov. 2, 2020, and U.S. Patent Application No.63/051,243, filed Jul. 13, 2020, each of which is hereby incorporated byreference in its entirety.

FIELD

The present disclosure relates to advanced yaw control of wind turbines.

BACKGROUND

Wind power is a major source of electricity with nearly 600 GW of globalinstalled capacity at the end of 2018. This is expected to increase tonearly 800 GW in 2021. However, operating wind power projects and windfarms continue to underperform on power output by 9% on average. This,coupled with much higher than expected unscheduled maintenance costscaused mostly by a high component failure rate, is leading to lowerrevenue and higher operating expense. The industry is further challengedby reduction in incentives and subsidies as power prices continue todrop. Therefore, there is significant demand for systems to augment orretrofit existing wind turbines to improve energy production.

Most of the time multiple wind turbines are installed in relativelyclose proximity to one another to facilitate use of areas with good windresources and efficient use of land, grid infrastructure and maintenancepersonnel. This collection of turbines is called a wind plant. As eachturbine in a wind plant extracts energy from the air moving past it, thewind speed is reduced and turbulence is increased downstream of theturbine. This region of reduced windspeed is called the wake of theturbine. It has been known for some time that wake interactions betweenturbines in a wind plant result in significant losses in production ofdownstream turbines. One technique for reducing the impact of wakes ondownstream turbines is to redirect the wakes away from those turbines byyawing the upstream turbine slightly away from perpendicular to thewind. This method of wake steering has been extensively studied in thescientific literature and is described in Brake and Scott and Obrecht.Typically, wake steering is attempted through a central control system.

A wind turbine is designed to convert mechanical power harvested fromthe air moving past the blades to electrical power. A typical windturbine will attempt to maximize its electricity output based onmeasurements of the relative wind direction taken using instrument(s)mounted on the back of the nacelle. If the relative wind direction isnot coming straight at the turbine within some predetermined relativewind direction range, then the turbine control unit will command the yawdrive to rotate until the relative wind direction is within the relativewind direction magnitude allowed. This system has several drawbacks: Theturbine control unit is using a limited amount of information collectedon the back of the nacelle, and ultimately it is always reactive ratherthan proactive. In addition, it has been shown that if an upwind turbinecompromises its power production slightly by adjusting its yaw angle tosteer wakes away from downwind turbines an increase in overall windfarmproduction is possible.

Most wind turbines as built do not have a mechanism to enable externalcontrol of the yaw position of the nacelle. In order to implement wakesteering or any other advanced yaw control method on a wind plant sometype of retrofit data communication and processing unit is required.Prior studies and systems have focused on implementing a dynamic offsetof the relative wind direction measured by the turbine control unit.

Furthermore, nacelle yaw alignment with respect to true north must becalibrated when the wind turbine is installed via visual inspection orsensor calibration. Unfortunately, this calibration often drifts overtime and re-calibration is required on a recurring basis. Discrepanciesin yaw alignment can lead to faulty functioning of control algorithmsthat rely on this signal, including wake steering.

Thus, there is a need for more advanced systems and methods of yawcontrol for wind turbines. There is also a need for methods and systemsthat provide external control of the yaw position of the nacelle.

SUMMARY

Embodiments of the present disclosure alleviate to a great extent thedisadvantages of known yaw control systems for wind turbines by closingthe loop on nacelle yaw position using a virtual relative wind directionsignal(s) to the turbine control unit and thus causing it to drive theyaw position to the desired optimum position. Disclosed systems andmethods have a distinct advantage over current methodology in that theydirectly achieve the desired nacelle yaw position without the need toaccount for localized rapid variation in wind direction measured on theback of the nacelle. This approach also enables enhancement of yaw driveperformance by responding faster or slower than the original turbinecontrol unit to changing conditions, and it enables inclusion ofadditional sensor information from other turbines and measurementdevices in determination of the optimum yaw angle of a turbine in agiven set of environmental conditions. Additional contemporaneousmeasurements of the wind direction and velocity from a plurality ofsensors in the region surrounding the retrofit turbine may becommunicated to the system and incorporated to determine a desirednacelle yaw position that will optimize performance of the wind plantoverall.

Embodiments of the disclosure are primarily intended to be employed as aretrofit system of an existing wind turbine as an enabling technology toallow wake steering, enhanced dynamic yaw optimization and collectiveyaw optimization algorithms to be implemented on a wind plant that wasnot originally built with these technologies. However, the techniquesdescribed for absolute nacelle yaw position measurement, closed loopnacelle yaw position control and dynamic nacelle yaw positionoptimization can also be incorporated into a new or retrofit datacommunication and processing unit directly. Exemplary embodiments usedistributed or edge computing and distributed resource control for yawcontrol of wind farms to facilitate wake steering and power outputoptimization.

An additional application of the technology described herein is thesystem identification and subsequent site-specific optimization of thenacelle yaw position behavior by adjusting the yaw control parameters inthe turbine control unit. These parameters may be adjusted so the systemworks optimally on own with its own sensors or with the virtual winddirection signal provided by the retrofit data communication andprocessing unit as a function of the nacelle yaw position commandsdetermined by the wind plant optimization controller. When the retrofitdata communication and processing unit does not receive a signalrepresenting optimum nacelle yaw direction or is otherwise disabled, therelative wind direction signal from the wind direction sensor on thenacelle is provided directly to the turbine control unit. Thus, theoptimal performance should be balanced when the turbine control unit isoperating using the wind direction sensor and when it is operating witha virtual wind direction signal to achieve a commanded nacelle yawposition.

Exemplary embodiments include a system for retrofitting a wind turbineto enable enhanced yaw control to improve wind turbine or wind plantperformance. An exemplary wind turbine includes a nacelle, a turbinecontrol unit, and one or more wind direction sensors attached to thewind turbine. An exemplary retrofit system for a wind turbine comprisesa retrofit data communication and processing unit configured to becommunicatively coupled to the turbine control unit. The retrofit datacommunication and processing unit receives a first signal representingan initial nacelle yaw position of the wind turbine and a second signalrepresenting a desired nacelle yaw position of the wind turbine. Theretrofit data communication and processing unit provides auxiliarycontrol over the wind turbine by disconnecting a relative wind directionsignal traveling between the wind direction sensors and the turbinecontrol unit, determining a virtual relative wind direction signal tocause the turbine control unit to drive the nacelle to the desirednacelle yaw position, and sending the virtual relative wind directionsignal to the turbine control unit instead of the relative winddirection signal.

In exemplary embodiments, the retrofit system detects a sensor orcommunication fault or a power failure, and the retrofit datacommunication and processing unit communicatively couples the winddirection sensors directly to the turbine control unit such that therelative wind direction signal is sent to the turbine control unit. Thewind direction sensors may continue to monitor relative wind directionafter the relative wind direction signal is disconnected from theturbine control unit. The wind turbine may further comprise a windspeedsensor connected to the wind turbine, and the retrofit datacommunication and processing unit intercepts and receives windspeedsignals from the windspeed sensor. The windspeed signal may be passed onto the turbine control unit unmodified or a virtual wind speedmeasurement may be generated to further modify the original turbinebehavior.

In exemplary embodiments, if the wind direction sensors and/or windspeedsensor fail, the retrofit data communication and processing unit enablesthe wind turbine to continue operation using outside signals generatedby additional wind turbines or additional sensors. The outside signalsmay be provided by the retrofit data communication and processing unitto the turbine control unit as virtual sensor signals. The retrofitsystem may further comprise two or more GNSS antennas and a differentialGNSS receiver attached to the wind turbine, and the initial nacelle yawposition may be determined using the differential GNSS receiver tocalculate a relative position vector between the two or more GNSSantennas.

An exemplary method of providing enhanced yaw control for a wind turbineincluding a nacelle, a turbine control unit, and one or more winddirection sensors attached to the wind turbine comprises receiving afirst signal representing an initial nacelle yaw position of the windturbine and receiving a second signal representing a desired nacelle yawposition of the wind turbine. Disclosed methods further comprisedisconnecting a relative wind direction signal traveling between the oneor more wind direction sensors and the turbine control unit. Exemplarymethods further comprise determining a virtual relative wind directionsignal to cause the turbine control unit to drive the nacelle to thedesired nacelle yaw position and sending the virtual relative winddirection signal to the turbine control unit instead of the relativewind direction signal so the turbine control unit drives the nacelle tothe desired nacelle yaw position.

In exemplary embodiments, when there is no signal received representingoptimal nacelle yaw position or desired nacelle yaw position, therelative wind direction signal from the one or more wind directionsensors is provided directly to the turbine control unit so the windturbine returns to the initial nacelle yaw position. Exemplary methodsfurther comprise disconnecting a wind velocity signal traveling to theturbine control unit and providing a virtual wind velocity signal to theturbine control unit.

In exemplary methods, the virtual relative wind direction signal isdetermined using a circular difference between the initial nacelle yawposition and the desired nacelle yaw position as feedback error in acontrol loop. The desired nacelle yaw position may be determined usingthe relative wind direction signal, a wind speed signal, and the firstsignal representing the initial nacelle yaw position. Exemplary methodsmay further comprise incorporating operating condition data from one orboth of: a plurality of additional wind turbine assemblies and aplurality of additional sensors to determine the desired nacelle yawposition. Disclosed methods may include automatically improving acontrol loop. Exemplary methods may further comprise preventing yawingof the wind turbine when the wind is not sufficient to start generatingpower.

In exemplary methods, the initial nacelle yaw position is determinedusing two or more Global Navigation Satellite System (GNSS) antennas anda differential GNSS receiver to calculate a relative position vectorbetween the two or more GNSS antennas. More particularly, the (GNSS)antennas may be mounted at a fixed distance apart on the nacelle and adifferential GNSS receiver may be used to determine a relative positionvector between the GNSS antennas. This relative position vectorprojected on the horizontal plane plus a fixed offset then provides anacelle yaw position signal which may be used directly or in combinationwith data from one or more additional sensors systems including anaccelerometer, gyroscope, magnetic compass, and SCADA data to determinethe nacelle yaw position signal relative to true north. Methods mayfurther comprise analyzing data from the GNSS antennas and thedifferential GNSS receiver in combination with the initial nacelle yawposition signal to estimate the initial nacelle yaw position.

Exemplary embodiments include methods of optimizing the performance of aturbine control unit comprising disconnecting wind direction signals andwind speed signals from a turbine control unit and introducing a seriesof virtual wind direction signals and wind speed signals into theturbine control unit. Next, an exemplary method comprises measuring yawposition responses of a nacelle of a wind turbine to the series ofvirtual wind direction signals, modifying parameters of the turbinecontrol unit, and repeating the series of virtual wind directionsignals. The methods may include predicting the yaw position responsesof the nacelle as a function of the series of virtual wind directionsignals and the parameters of the turbine control unit and performing anoptimization using historical operation data to reduce yaw movements andminimize errors between nacelle yaw position and wind direction.

Exemplary methods further comprise automatically generating parametercases to be run such that parameter space is covered with a minimumnumber of steps. Additional input signals may be simulated and providedto the turbine control unit. In exemplary methods, the wind turbine isrunning during performance of the methods and true relative winddirection is kept within a predetermined range. Exemplary methodsfurther comprise adjusting the parameters of the turbine control unit toachieve a desired nacelle yaw position when the turbine control unit isdisconnected from a wind direction sensor and responds to a virtual winddirection signal.

In exemplary embodiments, it may be necessary to tune the retrofit datacommunication and processing unit based on the existing turbine controlunit behavior to achieve the desired performance tracking the commandednacelle yaw position. The turbine control unit system identification andsubsequent tuning of the retrofit data communication and processing unittuning may be performed when installed on the wind turbine prior tonormal operation. Alternatively, in exemplary embodiments, the systemidentification and retrofit data communication and processing unittuning is performed or updated in a continuous automated processthroughout normal operation of the system. More particularly, additionalcontemporaneous measurements of the wind direction and velocity from aplurality of sensors in the region surrounding the retrofit turbine isincorporated to determine a desired nacelle yaw position that willoptimize performance of the wind plant overall.

Exemplary embodiments of the disclosure further provide systems andmethods of measuring nacelle yaw position using differential GPS/GNSS(Global Positioning System/Global Navigation Satellite System). Moreparticularly, the present disclosure describes using differentialGPS/GNSS for nacelle yaw direction measurement on wind turbines.Currently, differential GPS/GNSS is not utilized for nacelle yawdirection measurement on wind turbines. These techniques are used inother industries and such devices are often referred to as a “satellitecompass.” It should be noted that disclosed embodiments can utilize GPSand/or GNSS. Magnetometers which measure the earth's magnetic fieldcould also be utilized in this application in combination with or inplace of the differential GPS/GNSS system. Other instruments such asgyroscopes and accelerometers can also be utilized to further improvesignal resolution and time response and enable short durationride-through if the satellite signals are lost.

It should be noted that the embodiments and solutions described herein,when distributed and installed at a wind farm, come online, identifyeach other, and start working to optimize the wind farm operationautonomously, creating a “social” wind farm. Disclosed units “talk” witheach other over either a wireless or wired communication network and donot necessarily have any outside information. If any single turbine orunit goes down or is otherwise not functioning correctly, the remainderwould carry on without it. Optimization occurs through data sharing andarriving at a mutually agreed/beneficial optimization.

Accordingly, it is seen that advanced yaw control systems and methodsare described which provide a virtual relative wind direction signal(s)to the turbine control unit and thus cause it to drive the yaw positionto the desired optimum position. These and other features and advantageswill be appreciated from review of the following detailed description,along with the accompanying figures in which like reference numbersrefer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects of the disclosure will be apparent uponconsideration of the following detailed description, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of an exemplary embodiment of a wind plantin accordance with the present disclosure;

FIG. 2 is a side view of an exemplary embodiment of a wind turbinenacelle showing an exemplary retrofit system for a wind turbineincluding a retrofit data communication and processing unit installedbetween the existing wind direction sensor and the turbine control unitin accordance with the present disclosure;

FIG. 3 is a flow chart diagram of an exemplary embodiment of a retrofitsystem for a wind turbine in accordance with the present disclosure;

FIG. 4 is a schematic of an exemplary embodiment of a relay to ensurethat the turbine can continue to operate in the event of a communicationfault or loss of power in the retrofit system in accordance with thepresent disclosure;

FIG. 5 is a side view of an exemplary turbine nacelle in accordance withthe present disclosure with the addition of two GNSS antennas and adifferential GNSS receiver that computes the relative position vectorbetween the antennas to determine the current absolute nacelle yawposition of the turbine;

FIG. 6 is a top view of an exemplary nacelle in accordance with thepresent disclosure;

FIG. 7 is a flow chart of an exemplary control process for an exemplaryretrofit data communication and processing unit using the GNSS receiverto determine the current nacelle yaw position in accordance with thepresent disclosure;

FIG. 8 is a flow chart of an exemplary overall wind plant controlprocess as implemented in each turbine in accordance with the presentdisclosure;

FIG. 9 is a schematic of an exemplary embodiment of a centralized windplant controller to optimize the performance of the plant based on thesignals received from each turbine and retrofit data communication andprocessing unit;

FIG. 10 is a schematic of an exemplary embodiment of a decentralizedwind plant optimization scheme where each retrofit data communicationand processing unit communicates with every other retrofit datacommunication and processing unit and based on the signals from eachturbine determines the optimum position to drive its respective turbineto for the benefit of the overall wind plant;

FIG. 11 is a flow chart of an exemplary embodiment of a control processshowing the different control loop levels in the overall control;

FIG. 12 is a block diagram showing an exemplary embodiment of theinternal structure of a computer in which various embodiments of thedisclosure may be implemented;

FIG. 13 is a flow chart of an exemplary method used to identify theturbine data communication and processing unit nacelle yaw positionbehavior as a function of its parameters through synthetic input andsubsequent analysis;

FIG. 14 is an example of waveforms for sinusoidal variable frequencyinput virtual relative wind direction signal and a simple non-linearresponse nacelle yaw position; and

FIG. 15 is a flow chart showing an exemplary embodiment of a turbinecontrol unit parameter optimization process for nacelle yaw positioncontrol in accordance with the present disclosure.

DETAILED DESCRIPTION

In the following paragraphs, embodiments will be described in detail byway of example with reference to the accompanying drawings, which arenot drawn to scale, and the illustrated components are not necessarilydrawn proportionately to one another. Throughout this description, theembodiments and examples shown should be considered as exemplars, ratherthan as limitations of the present disclosure. As used herein, the“present disclosure” refers to any one of the embodiments describedherein, and any equivalents. Furthermore, reference to various aspectsof the disclosure throughout this document does not mean that allclaimed embodiments or methods must include the referenced aspects.

Embodiments of the present disclosure generally provide methods andsystems to modify the yaw position behavior of a wind turbine byintercepting the relative wind direction measurement signal between thesensor and the turbine control unit and providing a virtual winddirection signal to the turbine control unit to cause it to drive theyaw of the nacelle to the desired position.

An exemplary wind farm 1 is shown in FIG. 1 . A wind farm or wind plant1 includes a plurality of wind turbines 10. Each wind turbine 10includes a tower 11 and a rotor 12 and a nacelle 14 mounted to the topof the tower 11 along with a yaw bearing 9. The rotor 12 has a pluralityof rotor blades 16 coupled to and extending from a rotor hub 15. Therotor hub 15 is rotatably coupled to an electric generator 17 via themain shaft 3. FIG. 2 illustrates the major components in the nacelle 14.Various mechanical, electrical and computer systems, including but notlimited to, the electric generator 17, a gearbox 19, a yaw motor 7, anda turbine control unit 24, may be housed in the nacelle 14. A retrofitdata communication and processing unit 23 embodying the methodsdescribed in this disclosure may be added in the wind turbine.

An example flow chart of the information passing through an exemplaryretrofit system and method 20 is shown in FIGS. 3 and 4 . Typically,this system is implemented using electrical circuitry including a PLC orindustrial computer (FIG. 12 ) to perform the necessary calculations,determine if a fault state exists 31, and provide fault state digitaloutput 45. The retrofit system 20, also referred to as an auxiliary yawposition control system, implements advanced yaw control of the windturbine 10 and is communicatively coupled to the turbine control unit24. The system 20 includes a retrofit data communication and processingunit 23 to provide auxiliary control over the wind turbine 10. Inexemplary embodiments, the retrofit data communication and processingunit 23 is installed between the wind direction sensor or sensors 22 andthe turbine control unit 24.

The retrofit data communication and processing unit 23 receives a signalrepresenting the initial nacelle yaw position 27 of the wind turbine 10.The original cable 21 (dashed line) between the sensor(s) 22 and theturbine control unit 24 may be disconnected from the turbine controlunit 24 and connected to the retrofit system 20. This disconnects thevirtual wind direction signal 26 between the wind direction sensors 22and the turbine control unit 24. It should be noted that the winddirection sensors 22 may continue to monitor the relative wind directionafter the they have been disconnected from the turbine control unit 24.

A second cable 25 then connects the retrofit system 20 to the turbinecontrol unit 24 where it would normally receive the signal from the winddirection sensor 22. The retrofit data communication and processing unit23 determines 56 a virtual wind direction signal 26 to cause the turbinecontrol unit 24 to drive the nacelle 14 to the desired yaw position andcontinue operation of the wind turbine 10. The retrofit datacommunication and processing unit 23 receives the relative winddirection signal 39 from the sensor 22 and sends a virtual winddirection signal 26 determined from the current nacelle yaw position 27and the desired nacelle yaw position 29 of the turbine 10 to the turbinecontrol unit 24 in place of the relative wind direction signal 39. Asdiscussed in more detail herein, the desired nacelle yaw position 29 maybe computed using the relative wind direction, wind speed, and initialnacelle yaw position signals for the wind turbine 10 or based on aplurality of signals for the entire wind plant.

The virtual wind direction signal 26 provided by the retrofit system 20behaves like the original relative wind direction signal 39 from thesensor 22 to the turbine control unit 24 using the same communicationprotocol and scaling as the original system such that the turbinecontrol unit 24 cannot detect the difference. The above-describedsequence can be performed when there is no signal representing optimumnacelle yaw position so the wind turbine 10 returns to the initialnacelle yaw position. Dither or noise may be added to the virtual winddirection signal 26 as required to make it sufficiently realistic forthe turbine control unit 24.

Often wind direction measurements are combined with wind velocity andtemperature measurements in one device called a sonic anemometer. When asonic anemometer is used on a wind turbine, the retrofit system 20 alsoprovides the windspeed and temperature signals through to the turbinecontrol unit 24. A windspeed sensor could be provided, and the retrofitdata communication and processing unit 23 intercepts and receives thewindspeed sensor signals. Typically, these signals are passed throughunmodified. However, a virtual signal could be provided instead, forexample, to modify the turbine behavior or in the case of a failed winddirection sensor 22 on the turbine 10 by utilizing information fromanother source to provide the required information to the turbinecontrol unit 24. More particularly, if any of the sensors 22 fail, thewind turbine 10 can continue to operate using signals generated byadditional wind turbines 62 or additional sensors.

FIG. 4 shows the implementation of a relay circuit 28 to ensure that theactual signals from the relative wind direction sensor 22 on the turbine10 are available to the turbine control unit 24 in the event of a faultor loss in communication of the retrofit system 20. Multi-pole relaysand/or multiple relays may be used so that each required communicationwire passes through a separate circuit. Should a fault state occur, suchas a sensor or communication fault or a power failure, in exemplaryembodiments the wind direction sensors 22 are electrically connecteddirectly to the turbine control unit 24 so the relative wind directionsignal 39 measured on the turbine will be provided to the turbinecontrol unit 24 directly rather than the virtual wind direction signal26 produced by the retrofit data communication and processing unit 23.Depending on the fault state, the output 41 would be either the relativewind direction signal 39 or the virtual wind direction signal 26.

Referring now to FIGS. 5 and 6 , an exemplary approach to determine theabsolute nacelle yaw position is to measure the absolute nacelle yawposition directly using two or more GPS/GNSS antennas 30 positioned atsome distance from one another connected to a single receiver 32. Thereceiver 32 operates in what is referred to as differential GNSS modesuch that it computes the relative position of the two antennas 30 in aglobal framework based on the difference in the signal received fromeach satellite to each antenna. Differential GNSS is used in otherindustrial applications for determining the relative orientation andposition of different components and may be referred to as a satellitecompass, but nacelle orientation for a wind turbine 10 represents a newapplication of this technology. This technology enables determination ofa highly accurate relative position vector between the antennas 30 andthus determination of the nacelle yaw position to within about 1-degreeas long as the antennas 30 are placed a reasonable distance (0.5-2meters typically) apart.

Exemplary embodiments of mounting positions for these antennas are shownin FIGS. 5 and 6 where the antennas are shown axially aligned parallelwith the main shaft 3 of the wind turbine 10. However, the positions ofthe antennas could be varied depending on the conditions. The antennas30 may be placed at any known orientation relative to the main shaft andthe appropriate offset used in the control system 20 to determine thecurrent yaw position 27. For instance, they may be placed perpendicularto the main shaft 3 of the turbine 10 or at any known angle that can beaccounted for in the retrofit control system 20. In exemplaryembodiments, GNSS antennas 30 are mounted at a fixed distance apart onthe nacelle 14 and a differential GNSS receiver 32 is used to determinethe relative position vector between the GNSS antennas 30. This may bedone with a single GNSS receiver 32.

For the differential GNSS measurement of a wind turbine nacelle yawposition, antennas 30 may be mounted on a bracket that separates them aknown distance and aligns the axis with the turbine 10. Accuracy ofdirection measurement improves with horizontal distance between antennas30. Typically, 0.5-2 m is sufficient, 3 to 5 m is best and verticaldistance between antenna mounts should be minimized. The antennas 30 maybe mounted at any angle relative to the main shaft 3 (when viewed fromabove) as long as that angle is known and corrected for in software. Insome implementations mounting perpendicular to the main shaft 3 might bemore practical.

As shown in FIG. 7 , along with the relative position of the twoantennas 30 to determine nacelle yaw position, the GNSS receiver 32 mayalso provide a signal to the retrofit data communication and processingunit 23 or wind plant controller 64 indicating the position of theturbine 10 in global coordinates. This may then be used in the windplant optimization setup rather than pre-programming the turbinelocations. Additional instrumentation such as gyroscopes, accelerometersand magnetometers may be included to further improve the accuracy andreliability of the GNSS receivers 32. These signals may be used todetect and respond to other conditions on the turbine 10 such asexcessive tower vibration.

In exemplary embodiments, absolute nacelle yaw position measurement 50is performed using differential GNSS. For disclosed systems and methodsto work correctly, they must know the current nacelle yaw position(feedback) signal. The response of the nacelle can be measured by SCADAdata, gyroscopes, accelerometers, and/or differential GNSS. As discussedabove, exemplary embodiments employ two GNSS antennas 32 mounted acertain distance apart and connected to the same receiver 32 thatprocesses to calculate the vector between them. The two antennas 30 maybe built into a single device that positions them at a precise distanceapart, and then the entire device can be mounted on the turbine 10 atthe desired orientation. The differential GNSS system advantageouslyprovides the preferred <2 deg accuracy at an acceptable cost point. Itshould be noted that, in addition to measuring the nacelle yaw positionaccurately, the approximate location and altitude of the turbine 10could also be measured in this way.

In exemplary embodiments, the differential GNSS system data may beanalyzed to calibrate the nacelle yaw position measurement from SCADA,which may be a more reliable signal or both signals may be used incombination to determine the best current nacelle yaw position estimate.More particularly, the data from the GNSS antennas and the differentialGNSS receiver are analyzed in combination with the initial nacelle yawposition signal to estimate the initial nacelle yaw position.

Referring to FIGS. 8-11 , an exemplary wind plant optimization controlprocess implemented as an outer control loop 61 responds relativelyslowly to global changes in wind direction and determines the optimumnacelle yaw position for each turbine 10. This wind plant optimizationcontrol process may be incorporated into the retrofit data communicationand processing unit 23 or it may be a separate system that provides thedesired nacelle yaw position to the retrofit data communication andprocessing unit 23. A separate control process then incorporates amiddle loop 63 controller (FIG. 11 ). A middle loop 63 provides a winddirection signal to cause an inner loop 60 to drive the nacelle yawposition to that target nacelle yaw position. An inner loop controlprocess is the current turbine control unit 24 in the turbine 10 priorto the installation of the retrofit system 20 and drives the nacelle 14to a position where the relative wind direction signal 39 approacheszero.

Approaches for wind farm yaw optimization control systems have beendescribed elsewhere herein and, in general, incorporate the winddirection as determined from one or more nacelle-mounted wind sensors 22and the nacelle yaw position of those turbines 10 as well as the windspeed. Data from sensors 22 on the turbine 10 as well as from othersources may be combined to achieve the best possible information aboutthe wind throughout the wind plant 1. Other signals such as the poweroutput of each turbine 10 may also be used to adjust the optimizationshould a turbine 10 be shut down or curtailed.

An exemplary approach is to use a lookup table for wind speed anddirection to identify a predetermined desired nacelle yaw position foreach turbine 10. More complex processes may also be applied that furtheroptimize the plant performance based on localized difference in winddirection, rate of change of wind direction, and so forth. Theoptimization 64 may operate in a closed loop fashion where theprediction capability and thus the optimized solution improves over timeby accounting for the data collected. This optimization also needs toaccount for turbines 10 that are offline, curtailed to reduce poweroutput or are operating, but are not controllable. This may be detectedfrom the power signals and state of the retrofit data communication andprocessing unit 23 but additional signals such as turbine state may alsobe incorporated.

Determination of the desired nacelle yaw position may occur outside theretrofit data communication and processing unit 23, or it may beincorporated into its capabilities. The wind plant optimizationcontroller 64 may be implemented on a separate centralized controller(FIG. 9 ) or may be implemented as a distributed control scheme (FIG. 10) where each retrofit data communication and processing unit 23communicates the key information with the other systems and determinesthe optimum position for the turbine it is controlling based on thoseresults. This distributed control may be configured to continuefunctioning even if communication to one or more of the retrofit datacommunication and processing units 23 is lost.

Exemplary embodiments improve a control loop 63 by observing the turbinecontrol unit 24 response to relative wind direction signals 39 as afunction of time and, from these observations, modeling the behavior ofthe turbine control unit 24 to determine a series of virtual winddirection signals 26 to efficiently move the nacelle 14 to the desirednacelle yaw position 29. For the middle loop 63 to perform optimally, asystem identification of the existing turbine control unit 24 (innerloop 60) should be performed. This may be conducted experimentally bysetting different relative wind direction inputs and observing theresults, or it may be conducted using data collected over a period ofnormal operation of the turbine 10 using the variation from the winddirection.

Another application of exemplary embodiments includes preventingunnecessary yawing of a turbine 10 when the wind is not sufficient tostart generating power. Wind turbines 10 consume energy to yaw in lightwind conditions, and when an entire wind plant 1 activates its yawdrives simultaneously in light wind the power consumption can beconsiderable. With the auxiliary retrofit yaw control system 20installed, only a few sentry turbines 10 are rotated to face the winduntil they have sufficiently strong wind to start generating power. Thenthe remaining turbines are gradually yawed to face the wind and startproducing power. In this way the energy consumption of the wind plant 1may be reduced during periods of light wind.

A third application is to install the retrofit yaw control system 20temporarily to do a system identification and tuning optimization of theturbine control unit 24 process in the TCU. The turbine control unit 24is intended to keep the rotor 16 pointed into the wind based on feedbackmeasured from a wind vane or sonic anemometer(s) on the back of thenacelle 14. The challenge is that with many wind plants, the turbinecontrol unit algorithms or source code are not available to the plantowner or to a third party that seeks to optimize the settings. Whileturbine OEMs have developed and tuned the turbine control unit 24 for ageneric site, those settings are not necessarily optimum when oneconsiders the typical conditions at wind plants in with greater or lessturbulence than the generic site. If the turbine control unit 24 is tooactive, it will wear out yaw drive components quickly. It may alsocontinuously overshoot—moving to catch up to a shift in wind directionjust before the wind shifts back to where it was before. If it is notactive enough then significant energy production is lost because theturbine will operate at larger relative wind direction magnitudes thannecessary and in some cases may even suffer from threshold shutdownevents when the relative wind direction becomes too large, furtherreducing production.

While it is possible to tune a turbine control unit 24 by trial anderror, this takes a long time and may not provide optimal results. Somesettings may drastically reduce the performance of the turbine 10.Instead, disclosed embodiments determine the optimum parameters for theturbine control unit 24 in a simulated environment using real historicalhigh speed wind direction data measured on the turbines 10. Then thoseparameters can be entered directly to provide optimum performance. To dothis, we need an accurate model or simulation of the response of theturbine control unit 24 as a function of the input relative winddirection signal, the wind speed, and the adjustable parameters. Thisapplication provides a method for experimentally building a numericalmodel of the turbine control unit 24 that can be used to optimize theparameters for a particular turbine 10 or wind plant 1.

While turbine control unit yaw position control operates slowly, theinput signals are typically high frequency (10-25 Hz). These signals arethen filtered in some way. Unfortunately, for most turbines the rawinput is not recorded and may or may not have the required filteredsignals available in the SCADA data set. As the data is sampled slowly(often 10 or 20 second intervals) it can be impossible to develop amodel to predict the performance of the turbine control unit 24 andcorresponding nacelle yaw position as a function of time. Also, data forthe turbine control unit 24 with different parameters is not available.Thus, it is desirable to run a set of controlled experiments with knowninputs and various permutations of the relevant parameters in a shortperiod of time.

An exemplary approach is to use the retrofit data communication andprocessing unit 23 previously described to feed virtual relative winddirection and wind speed signals to the turbine control unit 24 andmeasure response. A GUI and/or wizard-like interface may be provided forrunning these experiments, including displaying and recording theparameters values which likely must also be manually entered in theturbine control unit 24 before each run. The device can be configured tomeasure yaw response directly rather than relying on SCADA data. Thiscould be done using an IMU or differential GNSS or a combination. Agyroscope can be used to measure the yaw system acceleration, whichrelates to forces on components and therefore their wear.

In exemplary embodiments, the relative wind direction signals 39 andwind speed signals are disconnected from the turbine control unit 24.Then a series of virtual wind direction signals 26 are introduced intothe turbine control unit 24 and the nacelle yaw position responses tothe virtual wind direction signals 26 are measured. Based on theseresponses, the parameters of the turbine control unit 24 can be modifiedto optimize performance. The series of virtual wind direction signals 26can be repeatedly sent to the turbine control unit 24. Exemplaryembodiments predict the nacelle yaw position responses as a function ofthe series of virtual wind direction signals 26 and the parameters ofthe turbine control unit 24. As discussed herein, the response of thenacelle 14 can be measured by SCADA data, gyroscopes, accelerometers,differential GNSS or any combination of these. Exemplary embodimentsautomatically generate a number of parameter cases to be run soparameter space is covered with a minimum number of steps. Theaccumulated historical operation data allows performance of optimizationto reduce nacelle yaw position movements and minimize the magnitude ofthe relative wind direction during operation.

Exemplary optimization methods are shown in FIGS. 13-15 and may bedescribed in the following steps:

Install the retrofit system 20 and ensure that turbine control unit 24is correctly communicating (this requires the system to behavecommunicatively exactly like the wind sensor 22 typically used by theturbine 10). The methods involve running 90 system identificationexperiments. If the turbine 10 is to be run during the experiments, thenthe real relative wind direction and wind speed would be measured by theretrofit system 20 and the output virtual relative wind direction signaladjusted to keep the actual relative wind direction magnitude within asafe range during the experiment.

Typically, a variation of frequency, amplitude and perhaps waveform(FIG. 14 ) of the input signal is required to identify the systembehavior. These trials may be run without the turbine 10 generatingpower or, if needed, with the turbine 10 generating power in relativelysteady conditions. Frequency range should go from the low end when theturbine 10 moves with the input signal to the high end where it does notmove at all. In exemplary embodiments, the wind turbine 10 is runningduring performance of the method and true relative wind direction iskept within a predetermined range.

Identify 70 the relevant turbine control unit nacelle yaw positionparameters and select the range of parameters. Generate (step 74)permutations of the parameters to be run and simulate 76 time history ofrelative wind direction and wind speed signals, including providing(step 82) new simulated values to the turbine control unit. Select 78the case and set and record 80 the parameters, including recording 84the current input signals and resulting nacelle yaw position. Repeat forvarious permutations of the available parameters. Record 80 each runinput and nacelle yaw position response along with the turbine controlunit 24 parameters used. For a given turbine control unit 24, it may bepossible to determine ahead of time the optimum combinations ofparameters to run to model the turbine control unit 24 in a minimumnumber of experimental runs. Random sampling algorithms such as Latinhypercube sampling can be used to minimize the number of experimentiterations while capturing the essence of the control behavior.

Develop the process to accurately predict the resulting nacelle movementas a function of the input parameters and relative wind directionsignal. This could be a machine learning model trained 92 based on theseresults to generate a numerical prediction of nacelle movement or insome cases an analytical model may be derived that provides an accurateprediction of the nacelle yaw position response.

Build and run 96 optimization simulation using actual plant data set 94to determine optimum parameters 99—can include cost function 98 for yawdrive wear along with energy production as part of total optimizationfor revenue.

Once an accurate model of the turbine control unit 24 as a function ofits parameters is defined, the turbine control unit 24 may alternativelybe optimized 99 to provide the best performance in combination with thewind plant controller 64 and middle control loop 63 on nacelle yawposition. As long as adequate performance is still achieved when theturbine 10 is operating without the relay activated to introduce theretrofit data communication and processing unit 23 then superiorperformance with the retrofit data communication and processing unit 23will yield superior performance of the entire wind farm 1 when allsystems are operating normally.

Potential variations of disclosure embodiments relate to input signals.For example, it is possible that other input signals will be used in theturbine control unit 24 and may be simulated and modeled in theapplication of these methods. These could include turbulence intensity(the variability of windspeed), temperature, power limit (curtailmentlevel), etc. Various test conditions, i.e., the turbine could be runningor in standby during the system identification. If running, then caremust be taken that the actual relative wind direction does not becometoo large. For scanning input signals, automated sequences or manualtesting could be employed. The method of measuring yaw response duringcharacterization testing could include, but is not limited to, SCADAdata, IMU, differential GPS, or some combination thereof. Optimizationcan be done for a particular turbine or site and for typical conditionsduring a portion of the year or over one or more entire years.

Exemplary embodiments use edge computing and distributed resourcecontrol for yaw control of wind farms 1 to facilitate wake steering andpower output optimization. These systems may communicate with each otherover either a wired or wireless network communication system. Thisadvantageously improves the power output across an entire wind farm 1 bycoordinating an individual turbine 10, avoiding the need for a singlecentral wind plant optimization processor. If an upwind turbinecompromises its power production slightly by adjusting its yaw angle tosteer wakes away from downwind turbines, an increase in overall windfarm production is possible. If one or more of the distributed systemsfaults or goes down, then the remaining systems can continue to optimizethe wind plant 1, thus providing robustness compared to a centralizedcontroller.

FIG. 12 shows an exemplary internal structure of a computer 1250 inwhich various embodiments of the present disclosure may be implemented.For example, the computer 1250 may act as a data analysis and augmentedcontrol system 20 as depicted in FIG. 3 . The computer 1250 contains asystem bus 1279, where a bus is a set of hardware lines used for datatransfer among the components of a computer or processing system. Bus1279 is essentially a shared conduit that connects different elements ofa computer system (e.g., processor, disk storage, memory, input/outputports, network ports, etc.) that enables the transfer of informationbetween the elements. Attached to system bus 1279 is I/O deviceinterface 1282 for connecting various input and output devices (e.g.,sensors, transducers, keyboard, mouse, displays, printers, speakers,etc.) to the computer 1250. Network interface 1286 allows the computer1250 to connect to various other devices attached to a network (e.g.,wind farm system 130, SCADA system, wind farm controller, individualturbine control units, weather condition sensors, data acquisitionsystem etc.).

Memory 1090 provides volatile storage for computer software instructions1292 (e.g., instructions for the processes/calculations described above,for example, receiving operating state information from the wind farmsystem and sensor data from the blade sensors to calculate cyclic loads,the processes for cycle counting, calculating the cyclic loads,determining the cyclic loading's effect on the life span of a windturbine or specific component thereof, the bending moment calculationsand calibration calculations) and data 1294 used to implement anembodiment of the present disclosure. Disk storage 1295 providesnon-volatile storage for computer software instructions 1292 and data1294 used to implement an embodiment of the present disclosure. Centralprocessor unit 1284 is also attached to system bus 1279 and provides forthe execution of computer instructions.

In an exemplary embodiment, the processor routines 1292 (e.g.,instructions for the processes/calculations described above) and data1094 are a computer program product (generally referenced 1292),including a computer readable medium (e.g., a removable storage mediumsuch as one or more DVD-ROMs, CD-ROMs, diskettes, tapes, etc.) thatprovides at least a portion of the software instructions for theinvention system. Computer program product 1292 can be installed by anysuitable software installation procedure, as is well known in the art.

In another embodiment, at least a portion of the software instructionsmay also be downloaded over a cable, communication and/or wirelessconnection. Further, the present embodiments may be implemented in avariety of computer architectures. The computer of FIG. 12 is forpurposes of illustration and not limitation of the present invention. Insome embodiments of the present disclosure, the data analysis andaugmented control system may function as a computer to perform aspectsof the present disclosure.

Thus, it is seen that advanced yaw control systems and methods areprovided. It should be understood that the example embodiments describedabove may be implemented in many different ways. In some instances, thevarious methods and machines described herein may each be implemented bya physical, virtual or hybrid general purpose computer having a centralprocessor, memory, disk or other mass storage, communicationinterface(s), input/output (I/O) device(s), and other peripherals. Thegeneral purpose computer is transformed into the machines that executethe methods described above, for example, by loading softwareinstructions into a data processor, and then causing execution of theinstructions to carry out the functions described, herein. Embodimentsmay therefore typically be implemented in hardware, firmware, software,or any combination thereof.

While embodiments of the disclosure have been particularly shown anddescribed with references to example embodiments thereof, it will beunderstood by those skilled in the art that various changes in form anddetails may be made therein without departing from the scope of theinvention encompassed by the appended claims. For example, the disclosedaugmented control is described in the context of wind farms and windturbines, but may be applied to augment control of other turbines, suchunderwater turbines.

What is claimed is:
 1. A method of providing enhanced yaw control for awind turbine including a nacelle, a turbine control unit, and one ormore wind direction sensors attached to the wind turbine, the methodcomprising: receiving a first signal representing an initial nacelle yawposition of the wind turbine; receiving a second signal representing adesired nacelle yaw position of the wind turbine; disconnecting arelative wind direction signal traveling between the one or more winddirection sensors and the turbine control unit; determining a series ofvirtual relative wind direction signals to cause the turbine controlunit to drive the nacelle to the desired nacelle yaw position; sendingthe series of virtual relative wind direction signals to the turbinecontrol unit instead of the relative wind direction signal such that theturbine control unit drives the nacelle to the desired nacelle yawposition; improving a control loop by making observations of responsesof the turbine control unit to relative wind direction signals as afunction of time; and modeling behavior of the turbine control unitbased on the observations; wherein the series of virtual relative winddirection signals is based on the modeling.
 2. The method of claim 1performing a system identification of the turbine control unit.
 3. Themethod of claim 2 wherein the performing of the system identificationcomprises setting different relative wind direction inputs and observingresults of the inputs.
 4. The method of claim 2 wherein the performingof the system identification comprises using data collected duringnormal operation of the wind turbine using variations from winddirection.
 5. The method of claim 1 further comprising preventing yawingof a plurality of wind turbines when the wind is not sufficient togenerate power.
 6. The method of claim 5 further comprising rotating asubset of the plurality of wind turbines to face the wind until thesubset of the plurality of wind turbines have sufficiently strong windto start generating power.
 7. The method of claim 6 further comprisingyawing the remaining wind turbines of the plurality of wind turbines toface the wind and start producing power.
 8. The method of claim 1further comprising calibrating the desired nacelle yaw position fromSCADA data using differential GNSS data to estimate the initial nacelleyaw position.
 9. The method of claim 8 wherein the calibrating is doneby analyzing differential GNSS data in combination with the initialnacelle yaw position signal to estimate the initial nacelle yawposition.
 10. The method of claim 1 comprising multiple wind turbinescommunicating with each other to provide auxiliary control over eachwind turbine by disconnecting a relative wind direction signal travelingbetween the one or more wind direction sensors and each respectiveturbine control unit, determining a virtual relative wind directionsignal to cause each respective turbine control unit to drive thenacelle to the desired nacelle yaw position, and sending the virtualrelative wind direction signal to the turbine control unit instead ofthe relative wind direction signal.
 11. A system of advanced yaw controlof a wind farm comprised of multiple wind turbines, each wind turbineincluding a nacelle, a turbine control unit, one or more wind speedsensors, and one or more wind direction sensors attached to the windturbine, the distributed system comprising: a retrofit datacommunication and processing unit configured to be communicativelycoupled to each turbine control unit; wherein the retrofit datacommunication and processing units identify each other and communicatewith each other to transmit data including a first signal representingwind direction measured as a sum of nacelle yaw position and relativewind direction measured by the one or more wind direction sensors, and asecond signal representing wind speed measured by the one or more windspeed sensors; wherein each retrofit data communication and processingunit measures an initial nacelle yaw position of each wind turbine;wherein the retrofit data communication and processing unitscollectively determine a desired nacelle yaw position for each windturbine; and wherein each retrofit data communication and processingunit provides auxiliary control over each wind turbine by disconnectinga relative wind direction signal traveling between the one or more winddirection sensors and each respective turbine control unit, determininga virtual relative wind direction signal to cause each respectiveturbine control unit to drive the nacelle to the desired nacelle yawposition, and sending the virtual relative wind direction signal to theturbine control unit instead of the relative wind direction signal. 12.The system of claim 11 wherein if one or more of the retrofit datacommunication and processing units are unable to communicate with eachother, any remaining retrofit data communication and processing unitscontinue to function.
 13. The system of claim 11 wherein the retrofitdata communication and processing units prevent yawing of a plurality ofwind turbines when the wind is not sufficient to generate power.
 14. Thesystem of claim 13 wherein a subset of the plurality of wind turbinesrotate to face the wind until the subset of the plurality of windturbines have sufficiently strong wind to start generating power. 15.The system of claim 14 wherein the remaining wind turbines of theplurality of wind turbines yaw to face the wind and start producingpower.
 16. The method of claim 11 the retrofit data communication andprocessing units calibrate the desired nacelle yaw position from SCADAdata using differential GNSS data to estimate the initial nacelle yawposition.
 17. The system of claim 16 wherein the retrofit datacommunication and processing units analyze differential GNSS data incombination with the initial nacelle yaw position signal to estimate theinitial nacelle yaw position.
 18. The system of claim 11 comprisingmultiple wind turbines communicating with each other to provideauxiliary control over each wind turbine by disconnecting a relativewind direction signal traveling between the one or more wind directionsensors and each respective turbine control unit, determining a virtualrelative wind direction signal to cause each respective turbine controlunit to drive the nacelle to the desired nacelle yaw position, andsending the virtual relative wind direction signal to the turbinecontrol unit instead of the relative wind direction signal.